1. Field of the Invention
A pinch valve for regulating, throttling or stopping the flow of a fluid.
2. Description of the Prior Art
Pinch valves are commonly used in the chemical process industry, food industry, mining, metallurgy, plating and indeed any industry where liquids containing solids, such as slurries, are made to flow. They are used for both on/off and flow control situations. The general distinctions and advantages of pinch valves over other types of valves are well known and recognized.
The basic construction of a pinch valve consists of a flexible resilient elastomeric sleeve installed in a fluid process line together with means to constrict the sleeve so as to regulate, throttle or terminate the flow of the fluid through the line.
Problems with leakage, ease and speed of installation and repair, verification of operability, cost and complexity of the valve have long been the subject of pinch valve design efforts.
Some pinch valves employ a mechanical pinch mechanism to constrict the sleeve. The majority of pinch valves manufactured today consist of a flanged elastomeric sleeve in which the sleeve is fitted either into a one-piece housing (by distorting the elastomer flange and pushing the sleeve into the housing) or more commonly, in a split housing with its associated sealing gaskets and bolts. The sleeve flange is outside the housing and is sandwiched between flanges on the housing and the line piping and serves to seal the valve against leakage of process fluids. Where adjustment of the valve is by a motive fluid, for example air or hydraulic fluid, which squeezes the intermediate portion of the sleeve, the flange also serves to seal the motive fluid.
Replacement of sleeves in prior art valves is time consuming. For example, in order to replace a damaged sleeve in a flanged pinch valve of the direct air actuated type, the air supply is disconnected, then flange bolts connecting the valve to the mating pipe flanges are removed. The valve is taken out of the piping system and the split valve housing opened in order to remove the sleeve. A new sleeve is placed in the housing and the housing bolted together with its attendant gasket sealing. The sleeve-housing assembly is then reinstalled into the piping system by bolting the valve flange to the pipe flanges, and reconnecting the air supply. Normally the new sleeve would then be proof-tested in the piping system to qualify the integrity of the sleeve.